Furnace



May 3, 1966 J. M. HEMINGWAY 3,249,076

FURNACE Filed Feb. 14, 1964 2 Sheets-Sheet l IIOV.AC

INVENTOR: JSE PH M. HE

y 1966 J. M. HEMINGWAY 3,249,076

FURNACE Filed Feb. 14, 1964 2 Sheets-Sheet 2 INVENTOR:

AT T Y JOSEPH M. HEMINGWAY l l/ n I no V.AC

FIGZ

United States Patent 3,249,676 FURNACE Joseph M. Hemingway, 14932 Avalon Ave, Dolton, Ill. Filed Feb. 14, 1964, Ser. No. 344,958 12 Claims. (Cl. 110-160) The invention relates generally to furnaces and more particularly to improvements in chimney construction and combustion conditions and to the control, discharge and dissipation of waste products of combustion from furnaces particularly of the industrial type where temperatures and the presence of metal corrosive gaseous elements are quite high.

Notwithstanding the use of chimneys for centuries, many smoke problems of importance remain. Additional problems have arisen where aircraft, municipal codes and built-up communities are involved. Although the use of tall chimneys is diminishing rapidly for draft and high altitude dissipation of waste products of combustion by aspiration, the forced ejection with short chimneys to drive the products of combustion high enough to prevent them from becoming a nuisance and health hazard still presents many unsolved problems including many involving combustion chamber conditions and intensely hot and corrosive by-product gases.

With all of the improved combustion efficiencies, and heat conservation in space heating applications, the stack temperature of the burned gases is comparatively low if combustion conditions can be kept constant. But, where incinerators, heat treating and the burning of industrial wastes are involved, the stack temepratures are quite high and chimney or liner corrosion is quite extensive. Moreover, intermittent operation, moisture variation, changes in draft pressures in fire boxes, radiation of stack heat into air conditioned spaces even through heat insulation, to mention a few, present many problems along with considerations of associated etfects on other equipment such as air conditioners, space cooling and cleanliness.

Of all the problems, the groups reltating to constancy of combustion conditions, longevity of the smoke stack structures, effect upon the fire box operation, and the nuisance and detrimental health effects on the environment and community play the biggest role in engineering objectives. On these points the provision of a standardized universal design is particularly desirable for many reasons. Economy and functional compliance with ordinances, good architectural uses, avoidance of expensive special designs, and alleviation of expert furnace room help regarding a wide variety of applications and uses comprise additional and worthy aims for manufacturers, service men, and users of smokestacks. Moreover, the amalgamation of soltuions for these many problems is a major consideration.

By way of a better understanding of the invention it may be noted that a constant negative pressure can be induced at all times in the fire box; the smokestack can be of a reduced diameter and can be made of thin wall tubing throughout its length; it is open without obstruction therein for a nonturbulent expulsion and propulsion of waste products of combustion at a low temperature high into the air; and, a thick refractory lining is used Where intense heat concentrations occur therein. These are major features.

It may be well to note at this time that for many years smokestacks serving boilers and incinerators have been made of ordinary hot roller steel and various types of stainless steel. Their longevity was problematical and replacements were often necessary in less than two years dut to the high heat and acids developed therein from the products of combustion, both of which attack the stainless as well as the hot rolled steel. Although in many installations a refractory material has been applied to the inside of the steel stack walls so that the products of combustion do not come in direct contact with the steel, and longevity is somewhat increased thereby, the refractory linings are quite thick and restrict the flow area at substantial expense. Moreover, they are subjected to various operating temperatures. Maximum boiler line gas temperatures average below 500 F whereas incinerator flue gases are often above 2000 F. Any elements in the stack exposed to such high temperatures constantly deteriorate rapidly. Moreover, rapid deterioration requires extra space and access for service convenience. Not only does warm-up and cool-off with these temperatures cause cracking and chipping, but the insulation material is required around the stacks that are built inside a building and increased clearances are required to combat a long recognized fire hazard to prevent a conflagration from this source. In this endeavor, exepnsive non-combustible insulation, extra-clearances or non-combustible shaft linings are used around the stacks. All of these items mean added expense. Forced draft conditions only aggravate the difiiculties.

The invention contemplates an improved refractory lined draft unit which produces, maintains, and controls a positive draft in a Smokestack or chimney at all times to prevent condensation at low temperatures and also vent the firebox of any boiler, incinerator or other type of furnace which requires venting irrespective of the character of the flue gases. A further object of the invention is to maintain a predetermined favorable fire box draft condition at all times, vital to complete flame combustion in any fire box regardless of atmospheric conditions and autogenous burning of objectionable gases which may escape flame combustion in the fire box. Back drafts and slow starts are also eliminated regardless of the length of the stacks.

The invention is further characterized in reducing stack temepratures and by maintaining a mild negative pressure in the fire box of an incinerator or other equipment, keeping the furnace room free from contamination by any partial combustion products, preventing flash-back when the charging door is opened, and of particular importance insuring proper combustion of the refuse or fuel with a resultant minimum emission of air polluting smoke and obnoxious gases.

A further object is to provide a unit that will utilize any source of air at any temperature in the stack without varying combustion conditions and will reduce stack flue gas temperatures 65% or more thereby preserving for all stacks a low substantially constant flue temperature under normal or abnormal working conditions with greatly increased stack life and exceedingly minimized fire hazards.

A further object of the invention is to provide an improved, less expensive stack construction to which thin wall steel tubing of uniform thickness throughout its length can be employed for venting boilers and the tubing can be weight-supported on the building structure at spaced levels for ready installation, service and repair at any level.

A further object is to keep the stack at a temperature below a corrosive point while maintaining improved combustion in the fire box and improved dissipation of more completely burned gases into the atmosphere.

These being among the objects of the invention, other and further objects will become apparent from the description of the drawings in which:

FIG. 1 is a diagrammatic showing of a furnace installation embodying the invention;

FIG. 2 is an enlarged sectional view through the lower stack portion in FIG. 1 showing a preferred embodiment of the invention;

FIG. 3 is a cross-sectional view taken on line 3-3 of FIG. 2;

FIG. 4 is an enlarged sectional View of the device for supporting the stack in sections at different levels upon the building structure; and

FIG. 5 is a circuit diagram of the essential electrical control connections of the invention.

For a better understanding of the description of the particular structure illustrated it may be well to note that the invention can be used with any conventional furnace having conventional air intake damper and fuel feed controls for heat or combustion control, and the present invention can be embodied in conventional stacks.

In the present invention a negative pressure is maintained in the fire box at all times or as required, by an air pressure from a blower effective for that purpose at the throat of a venturi located between the fire box and stack .or in the stack proper.

For incinerator or high heat application the amount of standard air put through the venturi can be varied with a shutter or air valve on the blower intake operated by a reversing motor controlled by a thermostat above the venturi. The intake to the blower can be opened more as the stack temperature exceeds a predetermined stack temperature and can be closed as the stack temperature drops below the predetermined temperature.

Irrespective of the blower output a negative pressure in the fire box can be kept constant by a variable shutter controlled air relief to atmosphere at a bypass opening between the venturi and fire box. The bypass shutter is operated by a reversing motor as controlled by a pressurestat exposed to fire box pressures and restricts the fiow area of the bypass when the negative pressure moves towards zero pressure and to enlarge the flow area when a deepening of negative pressure occurs.

Referring now to the drawings, more particularly a building is shown in FIG. 1 having vertically spaced floors 12 with concentric openings 13 through them walled in by partitions to form a shaft 14 to receive a chimney 16. The furnace 18 is located in the basement 20 where it is fired with conventional equipment either for space heating or burning refuse.

It will be appreciated that the stack and furnace can be variously located with respect to each other in different installations in which case T-sections and different breeching arrangements (not shown) can be used, but for purposes of illustrating the preferred embodiment for incinerator application, the outlet or vent 22 from the fire box 24 having a draft for combustion air at 25 is directly under and aligned with the shaft 14. In this arrangement a trap or service section 26 in the form of a refractory ring rests directly on the furnace at the vent 22 and an opening 29 vents the ring to atmosphere through a passage 28 (FIG. 3) in the refractory body. The opening 29 is closed by a shutter 30 having a fixed vent hole 32 therethrough and the shutter is moved by a reversing motor 34 through a gear box 36 to vary the opening 29 as controlled by a pressurestat 38 for low temperature furnaces such as boilers but as safeguarded by the thermostat to open wide above a certain temperature with medium temperature furnaces such as incinerators. The shutter is removable for inspection purposes. It will be observed (FIG. 3) that the shutter 30 is located out of the direct path of the flow of burned gases and having the openings 29 and 32 as described stagnation of any hot gases on its stack side is prevented, thus serving to maintain its body temperature below a damaging temperature even under conditions most adverse to it.

Resting on the ring section 26 is a cylindrical shell 40 made of steel. This shell is lined with a thick wall or coating of high temperature refractory concrete 42 molded to internal dimensions (ID) and shapes which provide a venturi-like passage 44 that satisfies the usual gas venturi formula for high efficiency in which, for instance, the entrance cone 46 defines an included angle of approximately 20. The length of this entrance cone is less than the major diameter and the included angle of the outlet cone 48 is approximately 10. However, the venturi construction is used in reverse, namely, what would be the piezometric vents 50 are pressurized and also angled to the axis of the passage to develop a negative pressure below the entrance cone 46. The term venturi is used as a matter of convenience to indicate the relationship herein described. The venturi is open at both ends and no obstructions are present therein.

Above the venturi the stack can be provided with a catalyst 49 for autogenous burning of obnoxious unburned gases that might be present in the flue gases. It preferably is made of Nichrome wire and is supported on the wall of the stack by insulators 51 as controlled by switch 53 manually or automatically. It is known that burnable gases with air can be induced to burn autogenously in contact with a catalytic agent such as a heated Nichrome wire. Such a catalytic agent is of the class of agents frequently described as primary absorption catalysts for they operate to increase the reaction rate by adsorbing one or more of the reactant gases on their surface by primary valence forces which effect an activation or deforming of the molecules which makes them more susceptible to combine with the other reactants.

A plenum 52 made of suitable material is marginally secured to the cylinder 40 and extends axially along the outer side thereof at the level of the venturi throat 47 or -a little lower to provide a crescent-like manifold 52 encircling the cylinder. The wide space at 54 is connected to the outlet of a blower housing 56 having a rotor 58 therein driven by a motor 60.

Interconnecting the plenum and venturi throat are a series of injection ducts 50 around and through the wall of the throat 42. As already mentioned, they are disposed at an acute angle to the axis of the venturi with respect to the upstream end thereof. This angle is approximately 30. The ports of the ducts are elongated in the wall of the venturi throat and arranged in two or more series of ports circumferentially around the venturi throat and with the ports in one series alternately spaced longitudinally from the ports in an adjacent series.

The ducts are thus disposed to direct air in an upward direction of flow in the throat. The air jets provided thereby induce flow of burned gases from the furnace fire box 24 and intimately mingle therewith as they pass through and beyond the throat.

It should be noted at this point that a single ring-typeport has heretofore been used located either above or below a venturi-like throat to induce a furnace draft. However, such are made of metal that is exposed to the hot gases and do not provide a controlled negative pressure producing power attained by the invention. In the present invention many sharp jets of air penetrate, drive and intermingle with the column of hot gases so quickly as to dilute the heat before any surface in the stack is contacted.

In the present invention the hot products of combustion therefrom contact only refractory material designed for maximum longevity at high heat under normal or abnormal oeprating conditions without any contact with metal outside of the fire box walls. The gate 30 even when closed is cooled by air passing through opening 32 and is inexpensive and in a readily accessible place for replacement if ever desired. It opens into a ceramic walled passage where the inflowing air buffets the high temperature burned gases so that any metal corrosive gases that might be present are greatly diluted next to the gate below corrosion danger.

Referring again to the blower 56, the intake 61 to the blower can be connected mainly to outside atmosphere. It should not take its full supply of air from the furnace room unless the furnace room is well opened to the atmosphere. Preferably, it draws air from the shaft 14 which can be open at the top to the atmosphere to assist in maintaining the shaft cool and not create a negative pressure in the furnace room. The intake 60 can be slightly open to the furnace room but only for ventilation purposes. Opening 32 also serves a similar purpose.

Preferably, the amount of working air taken in by the blower 56 can be controlled by a variable gate 64 operated through a gear reduction 66 with a motor 68 as con trolled by a thermostat 70 located on the stack above the sleeve 46.

The variable gate will not have a 100% shut-off. It has a port 72 that is continuously open, thereby permitting an air flow during the oif" period of the blower 56. The blower will be stopped by means of a switch activated at the minimum setting of the variable gate. A small capacity auxiliary blower 62 can be placed over the port 72 where the main blower had a high horse power motor to take over when the gate 64 to the main blower is closed and the thermostat 70 turns the main blower off. The auxiliary blower is then turned on by a relay 74 (FIG. 5) until the main blower is again turned on by the thermostat at which time the relay is de-energized to idle the auxiliary blower 62 and start the main blower.

It will be observed that the plenum and blower constitute a unit that can be applied to existing stacks or as original equipment in new stacks. It can be installed immediately beyond the outlet of the furnace or fire box in the breeching connection from the appliance to the stack or above the breeching entrance directly in the stack. It will be further noted that the entire unit can be used independently where automatic controls are not employed.

Referring to FIGS. 1 and 4, the support of the stack 16 in the shaft 14 is illustrated in which the stack is made up of tubular sections 80 in which the lower end 80:: of an upper one is aligned with the upper end 89b of a lower one.

A support ring and brackets 82 are fastened to a section in weight supporting relationship to be supported in turn on coil springs 84. The lower end of the springs rest on the floor edge or, depending on the size of the openings 13, in anti-slip cups secured to the floor with rivets 88 and an anchor ring 90 or steel members secured to the building frame work at spaced elevations.

The major weight of the stack is thereby distributed and each spring suspension unit takes a predetermined portion of the load. Thus, the need for a stack that is thick and heavy enough at the bottom to support the entire stack weight on a single foundation is eliminated. This is important also in the invention because non-corrosive conditions developed in the stack also eliminate the need for thick metal walls to combat corrosion. Wall thicknesses can be as small as 20l6 gauge sheet metal. Even with the expense of stainless steel the initial and upkeep cost is less than that conventionally experienced.

The support of the stack should not be by solid contact between supporting and supported elements. Building vibration and heat expansion differentials will overload certain portions or areas. However, with the present invention the lower sections are not affected if the stack is integrated at each joint because the precalculated weight is evenly distributed. Moreover, sections can be removed and replaced laterally through access doors in the shaft merely by jacking up several sections to free a lower one for removal in a minimum of space. Sections of various length supported at each floor will be found to be satisfactory in the architectural design of the building 10.

Once installed, adjustment for operation of the equipment preferably begins with the intake opening 61 of the blower 56 wide open, the conventional combustion air supply substantially open, and the shutter 30 on the bypass opening 29 closed. Under this condition the opening 32 is sized to barely maintain a desired minimum negative pressure in the fire box. Thereafter, with minimum volume flow through the stack with intake valve 61 closed and bypass shutter 30 open the control of the 6 shutter 30 motor 34 by the fire box pressurestat 38 is set for said minimum pressure and the thermostat 70 in the stack is set at above a minimum flue temperature around 240 F. which will prevent condensation in the stack with said computed flow volume. In this connection the maximum capacity of the blower is computed to provide less than 500 F. stack temperature under maximum heat production conditions and the fire box bypass valve closed at the combustion air draft pressure differential that is determined upon by the furnace manufacturer for maximum fuel consumption conditions. In operation it will be observed that the amount of air forced through the stack in addition to the burned gases is thus indexed to a predetermined negative pressure in the combustion chamber and to a predetermined flue gas temperature. With a furnace that is constant running during long periods of operation such as an incinerator as distinguished from intermittent space heat demand, the opening 32 can be a computed or empirically determined one as a fixed opening in which case the flue temperature is the controlling factor for the blower 56. But in any instance, the blower air is supplied in direct relationship to the production of heat by the intake motor 68 as controlled by the thermostat 70. The more fuel consumed, the greater is the production of heat urging the thermostat and blower to supply more outside air. The air entering at the venturi throat at an acute angle not only impels a power flow effect but quickly dilutes the by-products of combustion both thermally and chemically so that by the time the gases contact the walls of the stack beyond the venturi, practically all stack damaging effects of the burned gaess have been overcome and the steel stack does not require any further lining. In those instances where a catalytic agent 49 for autogenous burning of unburned obnoxious gases is used, the air mixed with the flue gases provides a combustible mixture for autogenous burning in which a blue flame low in infrared radiation waves occurs whose heat is carried upwardly and further mixed with cooling air rather than unduly heating the adjacent side walls of the stack. Moreover, the ultimate lay-products of combustion are propelled into the atmosphere to a safe height above the top of the stack as Well as diluting any somewhat opaque gases to a point of substantially invisibility. Moreover, the flue velocity can be as great as desired, as much as 60 per second or more without overdrafting the fire box. The bypass 30 merely opens wider to admit more cooling air to counteract any increase in fire box negative pressure.

It has been found that conventional devices producing positive pressure forced drafts for combustion air can be eliminated except those that are used in the atomization or the making :of a combustible air-fuel mixture of fluid fuels. Even there, a mild negative fire box pressure is a more favorable influence for combustion. With solid fuels and the burning of waste, com bustion is greatly improved by negative fire box pressure along with the economy of eliminating positive pressure devices. Many further advantages are also attained as set forth in the objects including a building that is free from furnace room odors and dust and a community free from smoke and combustion nuisances and hazards. These are in addition to the longevity of chimneys and a greatly reduced radiation and con duction of heat into a building from a stack located inside the building. Consequently, although all the benefits and functions are not clearly understood including the unexpected ejection height present with jet nozzles used as described with or without a venturi throat, but particularly with 'a venturi throat as described, it will be appreciated how the objects set forth are accomplished and how various and further changes and adjustments in the apparatus described can be made without departing from the spirit of the invention, the scope of which is commensurate with the appended claims.

What is claimed is:

1. A dissipator for burned gases from a fire box of a furnace having a temperature above 500 F. comprising sleeve means connected to the vent of the fire box and having a thick wall of a high temperature refractory material with a passage therethrough defining a venturi through which the hot gases of combustion pass, a series of circumferentially spaced jet conduits through the ceramic material opening into the throat of the venturi at an acute angle to the axis thereof, means for forcing a supply of air in a plurality of air jets under pressure through said conduits in an upward direction into the throat to induce a negative pressure in the fire box and a rapid mixture with said hot gases, chimney means connected to the outlet of the sleeve means, and control means for said air forcing means to vary said air supply to provide a mixture temperature below 500 and eject the mixture from the chimney at high velocity.

2. A hot flue gas cooler comprising a cylindrical sleeve means having a thick wall of high temperature refractory material with a passage therethrough defining a venturi, a series of circumferentially spaced jet conduits through the refractory material opening in the throat of the venturi at a sharp angle to the axis thereof, means for forcing a supply of air under pressure through said conduits into the throat, means connecting the inlet of said passage to a source of hot burned gases, means for connecting the outlet of said passage. to a chimney, and temperature responsive means in said chimney for controlling the operation of said air forcing means to maintain the temperature in said chimney above a dew point temperature and below 500 F.

3. A hot burned gas cooler for a furnace having a fire box with a vent opening comprising a cylindrical sleeve means having a thick wall of a high temperature refractory material with a passage therethrough defining a venturi, a chimney connected to said sleeve means, a series of circumferentially spaced jet conduits through the refractory material opening into the throat of the venturi at an acute angle to the axis thereof, means for forcing air through said conduits into the throat including a blower for inducing a negative pressure in the fire box, means connecting the venturi inlet of the sleeve means to the vent opening of the furnace including a refractory conduit section having a bypass opening to the atmosphere, a variable shutter closing said bypass opening, pressure responsive means controlling said shutter with respect to a negative pressure in the fire box, heat responsive means in said chimney for controlling the op-. eration of said air forcing means to inject air into burned gases passing through said venturi to reduce the temperature with respect to a predetermined temperature.

4. A hot lburned gas dissipater for a furnace having a fire box with a vent opening comprising a cylindrical sleeve means having a thick wall of a high temperature refractory material with a passage therethrough defining a venturi, a series of circumferentially spaced jet conduits through the refractory material opening into the throat of the venturi at an acute angle to the axis thereof, means for forcing air through said conduits into the throat including a blower for inducing a negative pressure in the fire box, means connecting the passage inlet of the sleeve means to the vent opening including a refractory conduit section having a bypass conduit opening to the atmosphere, a variable shutter controlling the flow of air through said bypass conduit, pressure responsive means controlling said shutter with respect to a negative pressure in the fire box, a chimney connected to the outlet of said passage, heat responsive means in said chimney for controlling the operation of said air forcing means to inject air into burned gases passing through said venturi to reduce the temperature in said chimney below a predetermined temperature, said chim- 8 ney including interengaging sheet metal stack sections connecting the passage to the atmosphere, means for weight supporting the sections independently at vertical spaced distances with the lowest one supported upon said sleeve means.

5. A hot burned gas dissipator for a furnace disposed in a building having a chimney shaft open at the top to atmosphere and having a fire box with a vent opening, said dissipator comprising a cylindrical sleeve means having a thick wall of a high temperature refractory material with a passage the-rethrough defining a venturi, a series of circumferentially spaced jet conduits through .the refractory material opening into the throat of the venturi at an acute angle to the axis thereof, means drawing air from said shaft and forcing it through said conduits into the throat including a blower inducing a negative pressure in the fire box, means connecting the inlet of the sleeve means passage to the vent opening of the furnace sheet metal chimney in said chimney shaft connecting the sleeve means passage to the atmosphere, heat responsive means in said chimney for controlling the operation of said air forcing means to inject air into burned gases passing through said venturi to reduce the temperature in the chimney below a predetermined temperature.

6. A hot burned gas dissipator for a furnace disposed in a building having a chimney shaft with supports therein at vertically spaced distances and having a fire box with a vent opening, said dissipator comprising a cylindrical sleeve means having a thick wall of a high temperature refractory material with a passage therethrough, a series of circumferentially spaced jet conduits through the refractory material opening into the passage at an acute angle to the axis thereof, means for forcing air through said conduits into the throat including a blower for inducing a negative pressure in the fire box, means connecting the inlet of said passage to the vent opening of the furnace including a refractory conduit section having a bypass opening to the atmosphere, a variable shutter closing said bypass opening, pressure responsive means controlling said shutter with respect to a negative gauge pressure in the fire box, intercommunicating sheet metal tubular stack sections in said shaft connecting said passage to the atmosphere, spring means weight supporting the sections at vertically spaced points on said supports, heat responsive means in said flue for controlling the operation of said air forcing means to inject air into burned gases passing through said venturi to reduce the temperature therein below a predetermined temperature.

7. The combination called for in claim 6 in which said stack sections are movable vertically with respect to one another on said spring means for separation and removal in said shaft.

8. A fire box pressure control for furnace comprising sleeve means connected to the vent of the fire box and having a wall with a passage therethrough defining a venturi, a series of circumferentially spaced jet conduits through the wall opening into the throat of the venturi at an acute angle to the axis thereof, means for forcing air through said conduits into the throat in an upward direction to induce a negative gauge pressure in the fire box, means intermediate the venturi and said vent for bypassing atmospheric air to the venturi ahead of said jet conduits, and means responsive to the pressure in said fire box for operating said intermediate means to bypass increased amounts of air to the venturi when the pressure in the fire box exceeds a predetermined negative gauge pressure.

9. A stack for a furnace having a burned gas vent for its fire box comprising sleeve means having a lining of a high temperature refractory material defining a walled passageway therethrough, a series of circumferentially spaced jet conduits through the refractory material opening into said passageway at an acute angle to the axis thereof, means for forcing a supply of air under pressure through said conduits into the passageway including a blower, means interconnecting said sleeve means and the burned gas vent and having a variable bypass opening to the atmosphere, chimney means connecting said sleeve means to the atmosphere, heat responsive means in said chimney means for controlling the operation of said air forcing means for varying said supply of air to maintain the temperature of the mixture of burned gases and air below a predetermined temperature, and means responsive to the pressure in said fire box below a predetermined negative pressure for controlling said bypass opening to admit varying amounts of air from the atmosphere to maintain predetermined negative pressure.

10. For use in a stack for a furnace having a burned gas vent from its fire box, a sleeve means comprising a cylindrical sheet metal member, a lining of a high temperature refractory material supported in said member defining a walled passage therethrough in communication with said vent for the passage of hot gases of combustion, a series of circumferentially spaced jet conduits through the refractory material opening upwardly at their outlets into said passageway at an acute angle of approximately 30 to the axis thereof, a plenum enclosing the inlets of said conduits blower means connected to said plenum for supplying air to said plenum to provide air jets from said conduits into said hot gases with rapid mixture therewith for inducing a negative pressure at the inlet of said passage and at said vent, heat responsive means at the outlet of said passage responsive to the tem perature of the mixture for controlling the operation of said air forcing means to vary said supply of air and maintain the temperature of the mixture of burned gases and air below a predetermined temperature.

11. The combination called for in claim 10 including a refractory conduit section at the inlet of said passage having an opening to the atmosphere for the admission of air for varying said negative gauge pressure.

12. The combination called for in claim 10 including a catalytic agent in the path of flow of said air and gas mixture at the outlet of said lining for a-utogenously burning unburned obnoxious gases in said gas mixture.

References Cited by the Examiner UNITED STATES PATENTS 2,397,870 4/1946 Kneass -460 X 3,068,812 12/ 1962 Hemeon 110-8 3,134,345 5/1964 King 110-460 FOREIGN PATENTS 204,796 5/ 1939 Switzerland.

KENNETH W. SPRAGUE, Primary Examiner. 

1. A DISSIPATOR FOR BURNED GASSES FROM A FIRE BOX OF A FURNACE HAVING A TEMPERATURE ABOVE 500* F. COMPRISING SLEEVE MEANS CONNECTED TO THE VENT OF THE FIRE BOX AND HAVING A THICK WALL OF A HIGH TEMPERATURE REFRACTORY MATERIAL WITH A PASSAGE THERETHROUGH DEFINING A VENTURI THROUGH WHICH THE HOT GASES OF COMBUSTION PASS, A SERIES OF CIRCUMFERENTIALLY SPACED JET CONDUITS THROUGH THE CERAMIC MATERIAL OPENING INTO THE THROAT OF THE VENTURI AT AN ACUTE ANGLE TO THE AXIS THEREOF,MEANS FOR FORCING A SUPPLY OF AIR IN A PLURALITY OF AIR JETS UNDER PRESSURE THROUGH SAID CONDUITS IN AN UPWARD DIRECTION INTO THE THROAT TO INDUCE A NEGATIVE PRESSURE IN THE FIRE BOX AND A RAPID MIXTURE WITH SAID HOT GASES, CHIMNEY MEANS CONNECTED TO THE OUTLET OF THE SLEEVE MEANS, AND CONTROL MEANS FOR SAID AIR FORCING MEANS TO VARY SAID AIR SUPPLY TO PROVIDE A MIXTURE TEMPERATURE BELOW 500* AND EJECT THE MIXTURE FROM THE CHIMMEY AT HIGH VELOCITY. 